Very small computing devices represent a new frontier in the computer security war. Mobile devices amplify existing security concerns while introducing a new set of risks, but most people have an incomplete understanding of the full range of threats and the measures to limit their exposure. Large and fast-growing numbers of people from all walks of life use smartphones and other mobile devices for a widening range of activities, including conducting financial transactions and exchanging other sensitive information.This explosion of mobile devices quickly erodes the control that institutions might otherwise have had. Mobile users also put privacy at risk when they share location information because knowing where individuals are—or where they are not—can be powerful information in the hands of stalkers, burglars, advertisers, and others. At the same time, the rising tide of awareness of security risks for mobile devices should benefit the security of all devices.